Abstract: Approximately 85% of PWR nuclear power plants are injected with zinc for the purpose of controlling radiation field（the most effective and economical） and alleviating primary water stress corrosion cracking（PWSCC）, which has been considered as a mature technology. Adding zinc to the new unit, especially during the hot state functional test, has less risk and better effect. For the zinc addition of old units, there are certain risks for the first two cycles of zinc injection, but the risk is controllable after years of study abroad. For the first zinc injection of power plant, the application research of the primary zinc injection technology unit can be divided into two stages: in the first stage, the data measurement and collection before zinc injection, the impact evaluation of primary zinc injection on the unit, and the study and determination of the primary zinc injection strategy; in the second stage, zinc injection related transformation and change implementation, zinc injection and data measurement and collection after zinc injection, zinc injection effect evaluation, etc. Among the domestic PWR nuclear power units, Units 1 ＆ 2 of Sanmen and Haiyang NPPshave started zinc injection during the hot state functional test（HFT）. The sample measurement and operation data collection and analysis show that the expected purpose and effect have been achieved.